Improvement in the electro-deposition of nickel



UNITED STATES PATENT OFFICEO,

ISAAC ADAMS, JR, OF BOSTON, MASSACHUSETTS.

IMPROVEMENT IN THE ELECTRO-DEPOS ITION OF NICKEL.

Specification forming part of Letters Patent No. 93,157Qdated August 3, 1869.

To all whom it may concern:

Be it known that I, ISAAC ADAMS, Jr., of Boston, in the State of Massachusetts, haveinvented or discovered certain newand useful Improvements in the Electro-Deposition of Nickel, of which the following is a specification.

It has long been well known that nickelpossesses certain qualities which would renderit of great value-in the artsif it could be readily and surely deposited by the battery in such a manner as to make these qualities available. These qpalities are. first, its infusibility; second, itsecolor, which is nearly that of silver; third, its hardness, which is nearly equal to that of steel, and by reason of which it resists wear and abrasion to a much greater degree thansilver; fourth, its powerof resistingoxidation and the tarnishing and corrosive effects of many gases and liquids.

The two last-named qualities render it for many purposes greatly superior. to silver, which it much resembles in appearance, for electroplating other metals, and for making articles of solid metal. To these advantages should .be added its cheapness as compared with silver;

It has long been known that nickel could be, deposited from certain solutions by electricity; but the character of the deposits has been such that the valuablc qualities of the metal could not be secured to such an extent as to render it practically useful for general purposes, I

The difficulties in the way of its deposition have arisen mainly from the character of the solutions employed and the nature of the nickel vised for anodes in the depositing-cell. I haye discovered the causes of certaindiificultiesy' in the practical deposition of this metalt and am able to remove them and to point ut methods of preparing solutions and the 001 ditions which they must satisfy and under which they must be used, so that solid coherent. tenacious and flexible nickel can be deposit d to any desired amount. I can thus render Zhte electro-dcposition of nickel practically 'vali able not only for electroplating other-metals, but for that branch of the art of electro-deplosition known as eleetrotypingthat is, the deposition of nickel upon asurfacc .not to remain upon it as a permanent coating,

but to be re moved and used independently of it.

My improvements relate,first,to the method of preparing certain solutions from which the nickel is to be deposited and to the properties and conditions which such solutions must pos; sess; second, to a method of preparing nickel plates for the anode of the depositing-cell;

In order to explain fully the nature of my invention, it is necessary to refer to certain facts relating to the electro-deposition of metals generally which have been long known.

It is well known that metals are deposited in three conditions-via, first, as a black powder; second, in a state called reguline metal-that is, in a condition which exhibits the ordinary qualities of the metal; third, in a hard crystalline condition.

that the metals should be deposited in the reguline state, the applications which are made of the powdery or crystalline deposits being very few.

There are two applications of the art of electro-deposition which are usually recognized as two distinct branches of the art ,and which embrace nearly all its practical uses. One is called electroplating, and consists in depositing a coating of one metal upon another metal to remain upon it as a permanent coating. The other application is called electrotyping, and consists in depositing one metal upon another, or upon a prepared surface of some other substanc e,from which it is to be removed to be used separately from the surface upon which the deposit is made. For each of these purposes the metal must be deposited in the reguline state.

It has long been known that the metals differ greatly in the facility with which they can be deposited by the electric current, especially in the regulinc form. So, also, different solutions of the same metal differ greatly in respect to the deposits which may be obtained if not imp ossible,to obtain adeposit of reguline metal under any circumstances. The -Q1 culty seems in some cases to be inherent in the, character of the solution itself. In other cases it is due to the presence of foreign elements, or to the density or temperature of the solution,or to the density of the current employed.

Difierent solutions also. differ greatly in the amount of metal which can be deposited with third, to the character of the deposits obtained.

For most purposes in the arts it is necessary from them. WVith some solutions it is difficult,

a given strength of current. Some solutions give a deposit of metal which is the full chemical equivalent of the electricity passing through thesolution,while others fall far below it. Solutions also differ within wide limits in respect to the intensity and density of the current required to give a reguline deposit. The differences in solution in these respects are of great importance with reference to the cost of depositing the metals. The higher the intensity required to effect the deposition of the metal the greater the cost, and it isobvious that the cost of thedeposit will increase in proportion as it falls short of the full amount due to the electricity passing through thesolution.

Another circumstance is of great importance in the depositing of metals. It often happens that a thin film may be obtained of one metal upon another, but that'the process of deposition cannot be carried on to such an extent as to obtain a coating of any appreciable thickness. As soon as the metal to be coated has received a mere film, the conditions are so changed that the deposit is practically stopped.

A characteristic of this filmy deposit is that, though the particles of the metal adhere separately to the metal on which the deposit is made, the deposit is so thin that the particles of the deposit have no such coherence among themselves as will allow the deposit to be removed from the surface on which it is deposited, nor will such a deposit afford any substantial protection against abrasion in the ordinary wear to which most plated articles are subjected, or to the action of corrosive agents. It is obvious, therefore, that it is impossible to make electrotype-plates from such deposits, and that such deposits are practically useless for most purposes to which electroplating, is applied.

Although it has long been known that nickel could be deposited to some extent from various solutions, yet I believe that prior to my improvements it has not been practicable to obtain deposits of. such character and thickness as are required for electrotyping or even for most of the purposes of electroplating.

The solutions from which nickel has been heretofore most successfully deposited are, I believe, the chloride of nickel, the cyanide of nickel and potassium, the double sulphate of nickel and ammonia, and the double chloride of nickel and ammonium. Ofthese solutions as heretofore prepared I believe the chloride is the best; but thedeposits obtained from it y are very far from what are required for the generahpnrnoses to which the electro-deposition metal may be applied.

As this solution is ordinarily prepared, it-is a good conductor of electricity as compared with most liquids, and the nickel is deposited from it freely, but in a spongy, brittle condition, and more or less mixed with the peroxide of nickel,which gives it a brownish appearance. The deposit has also a great tendency to accumulateon the edges of the plate on which it is made in nodules or warty protuberances. Therefore, although the deposits may be obtained of considerable thickness, they are practically useless for electrotyping or electroplating. Moreover, aportion of the electricity is expended in forming a subchloride of nickel, which falls to the bottom of the vessel as an insoluble precipitate. In consequence of this the solution is soon exhausted both of nickel and chlorine and the process of deposition stops. Even when this solution is formed in the best-known manner by subliming a pure nickel chloride, the deposited metal, though free from the oxide, and therefore white, is deposited in the brittle warty condition,accompanied with the precipitation of the subchloride.

The doublecyanide of nickel and potassium is a poor conductor of electricity,and requires a high battery-power. With a low batterypower very little metal can be deposited, and that little is accompanied with the deposition ofperoxide of nickel to such an extent as to be black or nearly black. \Vith a high battery-power a film of white nickel may be ob tained, but not thick enough to satisfy the ordinary requirements of electroplati ng. Neither of these solutions, so far as I have seen them used, gives for any great length of time the full equivalent of metal for tha electricity employed, and so'far as I have been able to discover these two solutions are'in herently incapable of giving a coherent tenacious flexible metalsuch as is required in the arts for electrotyping and electroplating.

Of the other two solutions named I believe that before my improvements the best results were obtained from the doublclchloride of nickel and ammonium; but the metal deposited from it is of such a character as to; be worthless when deposited to any appreciable thickness. It is accompanied with the deposit of peroxide, and is therefore black or brown. It is extremely liable to split up into thiin scales, which may be rubbed off even with the hand. This want of coherence and tenacitylunfits it for the requirements of the arts. The metal deposited from the double sulphate oif nickel and ammonia is substantially the same as the above, but it is not so easily obtained. If

with these solutions a battery-power is used of an intensity of two Grove cells, or therettbout, a white deposit may be obtained of con iderable thickness, but still with such a tendency to split up in scales that it is practical y use less, and neither solution gives thcfull quivalent due to the current. I have discovered, however, that the difficulties attending the use of these last-named solutions and th character of their deposits are not inherent in the nature of the solutions, but are dine to the in minute quantities of certain substance, which are generally,and, Ibelieve ,universally,

modes of preparing them, or to 7e presence employed in making them, or inyae reduction of the nickel used in making th m.

In order, therefore, to prepare these solutions in such a manner as to give the results I have reached, it is necessary to adopt processes in their preparation and observe precautions which shall either dispense with the use of these substances altogether or shall effectually remove them if they are employed, and which are wholly unnecessary in their preparation for any other use with which I am acquainted.

In preparing my solution I prefer to use pure nickel; but commercial nickel may be used. Commercial nickel almost always contains more or less of the reagents employed in the purification or manufacture of the metal, such as sulphate of lime, sulphide of calcium, sulphide of sodium or potassium, chloride of sodium, and alumina. When any of these substances are present, it is necessary to remove them. This can be done by melting the nickel or by boiling it in water containing at least one per cent. of hydrochloric acid.

The boilings must be repeated with fresh acid and water until the wash-waters give no indication of the presence of lime when treated withoxalatc of ammonia. When the metal is purified by melting, the foreign substances collect on the top of the melted nickel in the form of a slag, which can be removed mechanically.

If the nickel contains zinc, it should be melted in order to volatilize the zinc and drive 'it off.

The crucible in such case must not be closed so tightly as to prevent the escape of the zinc fumes.

If copper, arsenic, or antimony is present, in the nickel, it can be removed after the nickel is dissolved by passing sulphure'ted; hydrogen through the solution.

The acid to be used in dissolving the metal. 'eonsists of one part strong nitric acid, six

phuric acid sufficient to convert all the metal into sulphate is added, and the solution is then evaporated to dryness. The mass is then again dissolved in water and a much smaller quantity than before of sulphuric acid is added, and the whole again evaporated to dryness, the temperature being raised finally to a point not to exceed 650 Fahrenheit. This temperature is to be sustained until no more vapors of sulphuric aeidcan be detected. The resulting sulphate of nickel is pulverized and thoroughly mixed with about one-fiftieth of its weight of carbonate of ammonia,

and the mass again subjected to a graduallyincreasing temperature, not to exceed 650 Fahrenheit, until the carbonate of ammonia is entirely volatilized.

If any iron is present, the most of it will be converted into an insoluble salt, which may be removed by filtration. The resulting dry and neutral sulphate of nickel is then dissolved in water by boiling, and if any insoluble residue remains the solution is filtered.

From the weight of the nickel used before solution the amount of sulphuric acid in the dry sulphate can be calculated. This amount of sulphuric acid is weighed out, diluted with four times its weight of water, and saturated with pure ammonia or carbonate of ammonia. I prefer the former. This solution, if it is at all alkaline, should be evaporated until it becomes neutral to test-paper.

The sulphate of ammonia of commerce may likewise be used; but pure sulphate of ammonia is to be preferred. The two solutions of the sulphate of nickel and sulphate of ammonia are then united and diluted with sufficient water to leave one and a half to two ounces of nickel to each gallon of solution and the solution is ready for use.

\.The object of twice evaporating to dryness and raising the temperature to so high a degree is, in the first place, to drive ott" the excess of sulphuric acid, and, secondly, to convert the sulphate of iron, if it exists, into basic sulphate, which is quite insoluble in water.

In order to give the best results, it is necessary that the solution should be as nearly new tral as possible, and it should in no case be acid. I prefer to use the solution of aspecific gravity of about 1,052", (water 1,000,) though a much weaker or a still stronger solution may be used.

At temperatures above the ordinary the solution still gives good results, but is liable to be slowly decomposed.

An excess of sulphate of ammonia may be used to dilute the solution in cases whereit is desirable to have it contain much less than an ounce of nickel to the gallon.

In preparing the solution of the double chloride of nickel and ammonium the nickel is to be purified and dissolved in the same manner as is described for the previous solution; and itis to be freed from copper and other foreign matters in the same manner. The solution is then to be evaporated to dryness. It should be made as nearly anhydrous as possible. The salt is then placed in a retort and heated to a bright-red heat. The salt su'blimes and is collected in a suitable receiver, the earthy matter being left behind. The salt thus purified is dissolved in water and to the solution is added an equivalent quantity of po re chloride of ammonium. The solution is then ready for use. 'It may have a specific gravity of 1,050 to 1,100".

Of these two solutions I much prefer the double sulphate, as it gives a softer metal,

which can be polished or otherwise worked more readily than that obtained from the double-chloride solution.

The double'sulphate solution has this important advantage over any other solution with which I am acquainted-that it gives a deposit with a smooth surface which can be polished with comparatively little labor.

When the process is properly conducted, the deposit can be made much thicker than is ordinarily required for plating other metals before it acquiresa rough or matted surface. With a metal so hard as nickel this is a matter of great importance.

Another important part of my invention is the preparation of the nickel plates to be used as anodes in the depositing-cells. Almost all commercial nickel contains more or less copper, zinc, and arsenic, and the complete removal of all these metals would bea matter of great difficulty and expense, and yet it is necessary to remove them or in some way counteract or neutralize their influence. \Vhen these metals are present,'they are to some extent deposited with the nickel and seriously affect the character of the deposited nickel. Copper impairs its color and has a tendency to produce a gray hard deposit, less tenacious and coherent than pure nickel, more easily tarnished, and hard to polish. A very small amount of arsenic makes the nickel tarnish readily in the air. Zinc affects the deposited metal in much the same way as copper, and it also tends to cause the evolution of hydrogen at the cathode or negative pole, and thus interferes with the deposition of the nickel.

I have discovered that in my improved solntions the depositions of copper and arsenic when present with the nickel may be effectually prevented by combining iron with the nickel. The iron itself is almost wholly precipitated as a peroxide, and is not deposited with the nickel to a sufficient extent to injure the character of the deposit; neither does it injuriously affect the solution.

The effect of the iron upon the copper is either to prevent it from being dissolved, or, if dissolved, to immediately reduce it upon the anode, where it forms a coating which may be removed from time to time by scraping. The arsenic forms an insoluble precipitate with the persalt of iron. The amount of iron which should be combined with the nickel will vary with the amount of copper and arsenic present, and should be as nearly as possible the chem ical equivalent of the amountpresent of those metals. It can be combined with the nickel by introducing the proper quantity in small fragments into the crucible in which the nickel is melted. Sometimes commercial nickel has sufficient iron present to counteract the influence of the copper and arsenic.

When copper and zinc are present to any considerable extent in nickel, it maybe melted in a crucible and cast into plates for anodes without any serious difficulty, as it then melts at a temperature not much greater than the melting-point of cast-iron. The presence of cast-iron also facilitates the melting of nickel. Pure nickel is very hard to melt; butit may be melted without much difficulty by introducing into the crucible'carbon in a finelydivided state, or silica, or both, in the manner described in a patent granted to me May 25, 1869, and the presence of these substances in the nickel does not injure the solution. It is necessary to melt commercial nickel not only to cast it into plates for anodes and combine it with iron when copper and arsenic are present, but to remove any potash, soda, lime, or alumina left adhering to it in the process of eduction, these substances being removed, as before stated, as slag. When zinc is present, it will be removed to a great extent in the process of melting by volatilization unless the melting be done in atight vessel.

Having prepared the solutions and anodes as herein described, nickel may be readily deposited; but in order to carry on the deposition continuously it is necessary to observe certain precautions.

First. The use of a battery of too high an intensity must be avoided. An intensity of two Smee cells is sufficient. A high intensity decomposes the solution and liberates free am monia, thus rendering the solution alkaline andimpairing its value. Whenever the smell of free ammonia arises from the decomposingcell, the operator may be certain that the solution is being injured. It is important that the depositing shall not be forced by the use of too strong a current.

Second. It is important that great precautions should be used to prevent the introduction into the solution of even minute quantities of potash, soda, or nitric acid. When an article to be coated is cleaned in acid or alkaline water, or is introduced into it for any purpose, the greatest care must be taken to remove all traces of these substances before the article is introduced to the nickel solution, as

the introduction of the most minute quantities of acids or alkalies will surely be injurious. It is important that the solution be kept free from all foreign substances; but its purity from those above named is especially important.

Third. The anode of the depositingcell should present a surface to the action of the solution somewhat larger than the surface upon which the deposit is being made, particularl y in the double-sulphate solution. The reason is that nickel dissolves so slowly that if the exposed surface is not larger than the surface on which the deposit is made the solution will not keep saturated. On the other hand, if the anode is very much larger than the positive pole, it tends to give a deposit of black powder.

Fourth. If zinc is to be coated, it should first be coated with copper, as it is difficult to make nickel adhere to zinc, and there is danger that the zinc may be acted on and injure the solution.

With solutions and anodes thus prepared and used the deposition of nickel can be carried on continuously and almost as surely and certainly as the deposition of copper from the common sulphate solution, though the limits of the batterypower which may be used are narrower.

The metal deposited is compact, cohesive, and tenacious. It may be deposited of nearly uniform thickness over any surface, however large. The deposited metal is capable of being annealed by a heat below a low-red heat. It then becomes flexible, malleable, and duetile. The deposit may be made of any required thickness, either to furnish effectual protection to the metal on which it is deposited, or to be removed and used separately from the surface on which it may be deposited. Thus electrotype-plates of nickel may be produced either as copies of irregular surfaces which it is desired to reproduce, or as plane sheets of nickel, which, after being annealed, may be rolled, hammered, or spun into a variety of forms or articles.

The solutions also give the full equivalent of nickel for the electricity employed. Ibelieve deposits possessing these qualities were never produced except by means of my improvements.

I therefore claim- 1. The electro-deposition of nickel by-means of a solution of the double sulphate of nickel and ammonia, or a solution of the double chloride of nickel and ammonium, prepared and used in such a manner as to be free from the presence of potash, soda, alumina, lime, or nitric acid, or from any acid or alkaline reaction.

2. The use, for the anode of a depositingcell, of nickel combined with iron to prevent the copper and arsenic which may be present from being deposited with the nickel or from injuring the solution.

3. The methods herein described for preparing the solution of the double sulphate of nickel and ammonia and the double chloride of nickel and ammonia.

4. The electroplating of metals with a coating of compact, coherent, tenacious, flexible nickel of sufficient thickness to protect the metal upon which the deposit is made from the action of corrosive agents with which the article may be brought in contact.

5. The deposition of electrotype-plates of nickel to be removed from the surface on which the deposit is made and used separately therefrom.

The above specification of my said invention signed and witnessed at Boston this 2d day of July, A. D. 1869.

ISAAC ADAMS, JR. Witnesses:

CHAUNOEY SMITH, WILLIAM W. SWAN. 

